Method and apparatus for transmitting a discovery signal, and method and apparatus for receiving a discovery signal

ABSTRACT

A transmission method of a base station is provided. The base station generates a first discovery signal block including a first PSS (primary synchronization signal) and a first SSS (secondary synchronization signal). The base station generates a second discovery signal block including a second PSS and a second SSS. Also, the base station transmits the first discovery signal block and the second discovery signal block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/577,601, filed on Nov. 28, 2017, and allowed on Sep. 26, 2019, whichwas a National Stage application of PCT/KR2017/004261, filed on Apr. 21,2017, and claims priority to and the benefit of Korean PatentApplications No. 10-2016-0050325, filed on Apr. 25, 2016, No.10-2016-0070544, filed on Jun. 7, 2016, No. 10-2016-0103036, filed onAug. 12, 2016, and No. 10-2017-0051283, filed on Apr. 20, 2017, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a method and an apparatus fortransmitting/receiving a discovery signal.

BACKGROUND ART

A wireless communication system supports a frame structure according tothe technical specification. For example, a 3GPP (3rd GenerationPartnership Project) LTE (Long Term Evolution) system supports framestructures of three types. The frame structures of three types include atype 1 frame structure applicable to FDD (frequency division duplex), atype 2 frame structure applicable to TDD (time division duplex), and atype 3 frame structure for a transmission of a unlicensed frequencyband.

In a wireless communication system such as the LTE system, a TTI(transmission time interval) means a basic time unit with which anencoded data packet is transmitted through a physical layer signal.

A TTI of the LTE system is composed of one subframe. That is, a timedomain length of a PRB (physical RB (resource block)) pair as a minimumunit of a resource allocation is 1 ms. To support the transmission ofthe 1 ms TTI unit, a physical signal and a channel are mainly defined bya subframe unit. For example, a CRS (cell-specific reference signal) maybe permanently transmitted to every subframe, and a PDCCH (physicaldownlink control channel), a PDSCH (physical downlink shared channel), aPUCCH (physical uplink control channel), and a PUSCH (physical uplinkshared channel) may be transmitted for each subframe. In contrast, a PSS(primary synchronization signal) and an SSS (secondary synchronizationsignal) exist for every fifth subframe, and a PBCH (physical broadcastchannel) exists for every tenth subframe.

Meanwhile, in the wireless communication system, a technique fortransmitting/receiving the signal for a heterogeneous frame structurebased on a plurality of numerologies is required.

DISCLOSURE Technical Problem

The present invention provides a method and an apparatus fortransmitting/receiving a signal for a heterogeneous frame structurebased on a plurality of numerologies in a wireless communication system.

Technical Solution

According to an exemplary embodiment of the present invention, atransmission method of a base station is provided. The transmissionmethod of the base station includes: generating a first discovery signalblock including a first PSS (primary synchronization signal) and a firstSSS (secondary synchronization signal); generating a second discoverysignal block including a second PSS and a second SSS; and transmittingthe first discovery signal block and the second discovery signal block.

Time and frequency distances between a resource for the first PSS and aresource for the first SSS may be the same as time and frequencydistances between a resource of the second PSS and a resource for thesecond SSS.

The first discovery signal block may further include a first PBCH(physical broadcast channel), and the second discovery signal block mayfurther include a second PBCH.

Time and frequency distances between a resource for the first PSS and aresource for the first PBCH may be the same as time and frequencydistances between a resource for the second PSS and a resource for thesecond PBCH.

The generating of the second discovery signal block may include applyingTDM (time division multiplexing) between the first discovery signalblock and the second discovery signal block.

A time distance between the first discovery signal block and the seconddiscovery signal block may be determined based on a predefined firstvalue.

A time distance between a first PRACH block and a second PRACH block forPRACH (physical random access channel) reception of the base station maybe determined based on a predefined second value.

The first PRACH block and the second PRACH block may exist within a cellsearch bandwidth, which is a bandwidth of sub-bands occupied by thefirst discovery signal block and the second discovery signal block.

A resource occupied by the first discovery signal block may includecontinuous time domain symbols.

The first PSS may be temporally earlier than the first SSS within thefirst discovery signal block.

The transmission method of the base station may further includedetermining the time distance between a first PRACH block and a secondPRACH block for a PRACH (physical random access channel) reception ofthe base station.

The generating of the second discovery signal block may includedetermining the time distance between the first discovery signal blockand the second discovery signal block based on a traffic condition.

According to another exemplary embodiment of the present invention, atransmission method of a base station is provided. The transmissionmethod of the base station includes: generating at least one discoverysignal block including a PSS (primary synchronization signal) and an SSS(secondary synchronization signal); and allocating a part or all ofresources belonging to a predefined resource pool for a transmission ofa discovery signal to the at least one discovery signal block.

The at least one discovery signal block may be plural.

The transmission method of the base station may further includedetermining the time distance between the plurality of discovery signalblocks depending on a traffic condition.

The transmission method of the base station may further includeconfiguring a duration and a periodicity of a DMW (discovery signalmeasurement window) to a terminal so that the terminal receives the atleast one discovery signal block.

The configuring of the duration and the periodicity of the DMW mayinclude configuring the DMW periodicity as a larger value than aperiodicity value that is predefined for other terminals that are notconnected to the base station by RRC (radio resource control) andconfiguring the DMW duration as a smaller value than a duration valuethat is predefined for the other terminals when the terminal and thebase station are connected by the RRC.

The at least one discovery signal block may be plural.

The allocating may include transmitting a part among the plurality ofdiscovery signal blocks within the DMW.

The transmission method of the base station may further includearbitrarily determining the time distance between a plurality of PRACH(physical random access channel) blocks for PRACH reception of the basestation.

The transmission method of the base station may further includetransmitting at least one among a plurality of PRACH (physical randomaccess channel) formats to a terminal through a PBCH (physical broadcastchannel) included in a first discovery signal block among the at leastone discovery signal block.

The time distance between the plurality of discovery signal blocks maybe applied as the same value for each periodicity of a discovery signaloccasion.

According to another exemplary embodiment of the present invention, areception method of a terminal is provided. The receiving method of theterminal includes: determining a DMW (discovery signal measurementwindow); monitoring a PSS (physical synchronization signal) within theDMW; and selecting one among a plurality of PSSs when finding theplurality of PSSs corresponding to a plurality of discovery signalblocks within the DMW.

The determining may include determining a duration and a periodicity forthe DMW based on a predefined duration value and a predefinedperiodicity value when the terminal is not connected to a base stationby RRC (radio resource control).

The determining may include receiving configuration of a duration and aperiodicity for the DMW from a base station when the terminal isconnected to the base station by RRC (radio resource control).

The DMW periodicity configured by the base station may have a largervalue than the periodicity value that is predefined for other terminalsthat is not connected to the base station by the RRC.

The DMW duration configured by the base station may have a smaller valuethan a duration value that is predefined for the other terminals.

The reception method of the terminal may further include monitoring anSSS (secondary synchronization signal) or a PBCH (physical broadcastchannel) included in a first discovery signal block corresponding to theselected PSS.

The selecting may include selecting a PSS having a best receptionperformance or satisfying a predefined reception performance conditionamong the plurality of PSSs.

Advantageous Effects

According to an exemplary embodiment of the present invention, thetransmitting/receiving method and the apparatus thereof for theheterogeneous frame structure based on the plurality of numerologies canbe provided.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a type 1 frame structure of an LTE system.

FIG. 2 is a view showing a type 2 frame structure of an LTE system.

FIG. 3 is a view showing a carrier raster and a carrier allocation basedon a method M101 or a method M102 according to an exemplary embodimentof the present invention.

FIG. 4 is a view showing a case in which a plurality of numerologies areused in a common frequency band.

FIG. 5 is a view showing a carrier raster and a carrier allocation basedon a method M112 or a method M113 according to an exemplary embodimentof the present invention.

FIG. 6 is a view showing a synchronization signal resource region basedon a method M201 according to an exemplary embodiment of the presentinvention.

FIG. 7 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal based on a method M202according to an exemplary embodiment of the present invention.

FIG. 8 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal based on a method M203according to an exemplary embodiment of the present invention.

FIG. 9 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal based on a method M210according to an exemplary embodiment of the present invention.

FIG. 10 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal for a carrier composed of aplurality of numerologies according to an exemplary embodiment of thepresent invention.

FIG. 11 is a view showing a constituent element of a discovery signalaccording to an exemplary embodiment of the present invention.

FIG. 12 is a view showing a resource configuration of a discovery signaloccasion based on a method M300 according to an exemplary embodiment ofthe present invention.

FIG. 13 is a view showing a resource composition of a discovery signaloccasion based on a method M310 according to an exemplary embodiment ofthe present invention.

FIG. 14 is a view showing a case in which a TDM is applied betweensignal blocks in a method M300 or a method M310 according to anexemplary embodiment of the present invention.

FIG. 15 is a view showing a case in which a discovery signal occasion istransmitted in a discovery signal measurement window according to anexemplary embodiment of the present invention.

FIG. 16 is a view showing a discovery signal and a PRACH resourcecomposition based on a method M310 according to an exemplary embodimentof the present invention.

FIG. 17 is a view showing a discovery signal and a PRACH resourcecomposition based on a method M320 and a method M330 according to anexemplary embodiment of the present invention.

FIG. 18 is a view showing a discovery signal and a PRACH resourcecomposition based on a method M321 and a method M331 according to anexemplary embodiment of the present invention.

FIG. 19 is a view showing a computing apparatus according to anexemplary embodiment of the present invention.

MODE FOR INVENTION

In the following detailed description, only certain exemplaryembodiments of the present invention have been shown and described,simply by way of illustration. As those skilled in the art wouldrealize, the described embodiments may be modified in various differentways, all without departing from the spirit or scope of the presentinvention. Accordingly, the drawings and description are to be regardedas illustrative in nature and not restrictive. Like reference numeralsdesignate like elements throughout the present specification.

In the present specification, redundant description of the sameconstituent elements is omitted.

Also, in the present specification, it is to be understood that when onecomponent is referred to as being “connected” or “coupled” to anothercomponent, it may be connected or coupled directly to another componentor be connected or coupled to another component with the other componentintervening therebetween. On the other hand, in the presentspecification, it is to be understood that when one component isreferred to as being “connected or coupled directly” to anothercomponent, it may be connected or coupled to another component withoutthe other component intervening therebetween.

It is also to be understood that the terminology used herein is only forthe purpose of describing particular embodiments, and is not intended tobe limiting of the invention.

Singular forms are to include plural forms unless the context clearlyindicates otherwise.

It will be further understood that terms “comprises” or “have” used inthe present specification specify the presence of stated features,numerals, steps, operations, components, parts, or a combinationthereof, but do not preclude the presence or addition of one or moreother features, numerals, steps, operations, components, parts, or acombination thereof.

Also, as used herein, the term “and/or” includes any plurality ofcombinations of items or any of a plurality of listed items. In thepresent specification, ‘A or B’ may include ‘A’, ‘B’, or ‘A and B’.

In the present specification, a terminal may indicate a mobile terminal,a mobile station, an advanced mobile station, a high reliability mobilestation, a subscriber station, a portable subscriber station, an accessterminal, user equipment, and the like, or may include whole or partialfunctions of the mobile terminal, the mobile station, the advancedmobile station, the high reliability mobile station, the subscriberstation, the portable subscriber station, the access terminal, the userequipment, and the like.

Also, in the present specification, a base station (BS) may indicate anadvanced base station, a high reliability base station (HR-BS), a nodeB, an evolved node B (eNodeB), an access point, a radio access station,a base transceiver station, a mobile multihop relay (MMR)-BS, a relaystation executing a base station function, a high reliability relaystation executing a base station function, a repeater, a macro basestation, a small base station, and the like, or may include whole orpartial functions of the advanced base station, the HR-BS, the nodeB,the eNodeB, the access point, the radio access station, the transceiverbase station, the MMR-BS, the relay station, the high reliability relaystation, the repeater, the macro base station, the small base station,and the like.

FIG. 1 is a view showing a type 1 frame structure of an LTE system.

One radio frame has 10 ms (=307200T_(s)) length and consists of tensubframes. Here, T_(s) is a sampling time and has a value of T_(s)=1/(15kHz*2048). Each subframe has the length of 1 ms, and one subframeconsists of two slots of 0.5 ms length. One slot consists of seven timedomain symbols (for example, an OFDM (orthogonal frequency divisionmultiplexing) symbol) in a case of a normal CP (cyclic prefix), andconsists of six time domain symbols (for example, the OFDM symbol) in acase of an extended CP. In the present specification, the time domainsymbol may be the OFDM symbol, or an SC (single carrier)-FDMA (frequencydivision multiple access) symbol. However, this is merely an example,and an exemplary embodiment of the present invention may be applied in acase in which the time domain symbol is the OFDM symbol or a differentsymbol from the SC-FDMA symbol.

FIG. 2 is a view showing a type 2 frame structure of an LTE system.

A relationship between the radio frame, the subframe, and the slot andeach length thereof are the same as the case of the type 1 framestructure. As a difference between the type 2 frame structure and thetype 1 frame structure, in the type 2 frame structure, one radio frameconsists of a downlink (DL) subframe, an uplink (UL) subframe, and aspecial subframe.

The special subframe exists between the downlink subframe and the uplinksubframe, and includes a DwPTS (downlink pilot time slot), a GP (guardperiod), and an UpPTS (uplink pilot time slot).

One radio frame includes two special subframes in a case in which adownlink-uplink switching periodicity is 5 ms, and includes one specialsubframe in a case in which the downlink-uplink switching periodicity is10 ms. In detail, FIG. 2 shows a case in which the downlink-uplinkswitching periodicity is 5 ms, and subframe 1 and subframe 6 are thespecial subframes.

The DwPTS is used for cell search, synchronization, or channelestimation. The GP is a period for removing an interference generated inthe uplink of the base station due to a multipath delay difference ofthe terminals. In the UpPTS period, the transmission of the PRACH(physical random access channel) or the SRS (sounding reference signal)is possible. The wireless communication system according to an exemplaryembodiment of the present invention may be applied to various wirelesscommunication networks. For example, the wireless communication systemmay be applied to a current wireless access technology (RAT: radioaccess technology)-based wireless communication network, or the 5G andbeyond 5G wireless communication networks. The 3GPP develops a newRAT-based 5G technical specification satisfying IMT (InternationalMobile Telecommunications)-2020 requirements, and this new RAT isreferred to as NR (new radio). In the present specification, forconvenience of description, the NR-based wireless communication systemis described as an example. However, it is merely an example, thepresent invention is not limited thereto, and the present invention maybe applied to various wireless communication systems.

As one among differences between the NR and a conventional 3GPP system(for example, CDMA (code division multiple access), LTE, etc.), NR usesa wide range of frequency bands in order to increase the transmissioncapacity. Related to this, the WRC (World RadiocommunicationConference)-15 hosted by the ITU (International Telecommunication Union)determined a WRC-19 agenda, and the WRC-19 agenda includes considerationof a 24.25-86 GHz band as the candidate frequency band for the IMT-2020.The 3GPP considers the frequency band from 1 GHz or less to 100 GHz asthe NR candidate frequency band.

As a waveform technology for the NR, OFDM (orthogonal frequency divisionmultiplexing), filtered OFDM, GFDM (generalized frequency divisionmultiplexing), FBMC (filter bank multicarrier), UFMC (universal filteredmulticarrier), etc. are being considered as the candidate technology.

In the present specification, as the waveform technology for thewireless access, a case using a CP-based OFDM (CP-OFDM) is assumed.However, this is merely for convenience of explanation, the presentinvention is not limited to the CP-OFDM, and it can be applied tovarious waveform technologies. In general, in a category of the CP-OFDMtechnology, the CP-OFDM technology applied with windowing and/orfiltering or spread spectrum OFDM technology (for example, DFT-spreadOFDM) is included.

Table 1 below represents an example of an OFDM system parameterconfiguration for the NR system.

In Table 1 (an example of the OFDM system parameter configuration), thefrequency band of 700 MHz-100 GHz is divided into three regions (i.e., alow frequency band (−6 GHz), a high frequency band (3-40 GHz), and asuper high frequency band (30-100 GHz)), and different OFDM numerologiesfrom each other are applied to each frequency band. In this case, one ofmain factors determining subcarrier spacing of the OFDM system is acarrier frequency offset (CFO) suffered by a receiving terminal. Thecarrier frequency offset (CFO) has a characteristic that it increases inproportion to the operation frequency due to a Doppler effect and aphase drift. Accordingly, to block performance degradation by thecarrier frequency offset, the subcarrier spacing must be increased inproportion to the operation frequency. In contrast, if the subcarrierspacing is very large, there is a drawback that a CP overhead increases.Accordingly, the subcarrier spacing must be defined as an appropriatevalue considering the channel and the RF (radio frequency)characteristic for each frequency band.

The subcarrier spacing of SETs A, B, and C of Table 1 is 16.875 kHz,67.5 kHz, and 270 kHz, respectively, which is approximately inproportion to a target operation frequency, and is configured to make adifference of four times.

TABLE 1 Set A Set B Set C Carrier frequency Low freq. High freq. (3-40GHz) Very high freq. (−6 GHz) (30-100 GHz) Subcarrier 16.875 kHz 67.5kHz 270 kHz spacing CP overhead 5.2% 5.2% 5.2% Number of 16 64 256 OFDMsymbols per 1 ms

Meanwhile, the values of the subcarrier spacing used in Table 1 aremerely exemplary, and the subcarrier spacing may be designed with asmany other values as necessary. For example, 15 kHz of the conventionalLTE subcarrier spacing is used as a base numerology, and the subcarrierspacing (for example, 30 kHz, 60 kHz, 120 kHz, 240 kHz, etc.) scaledwith multiplication by power of two based on this may be used for thenumerology scaling. This is illustrated in Table 2 (as an example of theOFDM system parameter configuration). To configure the subcarrierspacing to make the difference by multiplication by power of two betweenthe subcarrier spacing of the heterogeneous numerologies may beadvantageous to the operation (for example, carrier aggregation, dualconnectivity, or multiplexing of the heterogeneous numerologies withinone carrier) between the heterogeneous numerologies.

TABLE 2 Set A Set B Set C Set D Set E Subcarrier spacing 15 kHz 30 kHz60 kHz 120 kHz 240 kHz CP overhead 6.7% 6.7% 6.7% 6.7% 6.7% Number ofOFDM 14 28 56 112 224 symbols per 1 ms

One numerology may be basically used for one cell (or one carrier), andmay be used for a special time-frequency resource within one carrier.The heterogeneous numerology may be used for the different operationfrequency bands from each other as illustrated in Table 1, and may beused to support different service types from each other in the samefrequency band. As an example of the latter, the SET A of Table 1 can beused for the eMBB (enhanced mobile broadband) service of the 6 GHz bandor less, and the SET B or the SET C of Table 1 can be used for the URLLC(ultra-reliable low latency communication) service of the 6 GHz band orless. Meanwhile, to support the mMTC or the MBMS (multimedia broadcastmulticast services) service, the numerology having the smallersubcarrier spacing than that of the subcarrier spacing of the basicnumerology may be used. For this, in a case in which the subcarrierspacing of the basic numerology is 15 kHz, the subcarrier spacing of 7.5kHz or 3.75 kHz may be considered.

Hereinafter, the method and the apparatus for transmitting the signalfor the heterogeneous frame structure based on the plurality ofnumerologies in the wireless communication system will be described.

[Carrier Raster]

To discover a cell (or a carrier) in initial cell search process, aterminal must be able to detect the synchronization signal of thecorresponding cell for all candidate frequencies on the carrier rasterin the frequency band to which the corresponding cell belongs. Thesynchronization signal may be transmitted with reference to onefrequency among the candidate frequencies. For example, in the LTEsystem, the carrier raster spacing is 100 kHz, and the DC (directcurrent) subcarrier as the center of the subcarriers to which thesynchronization signal is transmitted is aligned on a specificgraduation point of the carrier raster.

When the detection of the synchronization signal is successful, theterminal may derive the center frequency position of the cell (thecarrier) from the frequency value of the corresponding carrier rastergraduation point. In the case of the LTE system, since the centerfrequency of the synchronization signal and the center frequency of thecell (or the carrier) are the same, the terminal may obtain the centerfrequency of the cell (or the carrier) without help of the base station.

On the other hand, to increase the frequency resource utilizationefficiency, the new carrier raster may be designed. Next, the carrierraster may mean a group of the candidate reference frequencies of thesynchronization signal or may mean a group of the candidate centerfrequencies of the cell (or the carrier). The former and the latter cangenerally be separated from one another.

In a case of an intra-band contiguous carrier aggregation, to minimizethe idle band inevitably generated between the carriers, the frequencyspacing of the carrier raster may be determined as an integer multipleof the subcarrier spacing. This is referred to as a method M100.

Also, when it is assumed that one resource block consists of N resourceelements in the frequency domain, the raster spacing may be determinedas an integer multiple of the multiplication of the subcarrier spacingand N. This is referred to as a method M101. For example, the spacing ofthe carrier raster for a frequency band using the numerology having asubcarrier spacing of 15 kHz may be a multiple of 15 kHz by the methodM100. In this case, if N=12 is assumed, the raster spacing may be amultiple of 180 kHz or may be 180 kHz itself by the method M101.

FIG. 3 is a view showing a carrier raster and carrier allocation basedon a method M101 or a method M102 according to an exemplary embodimentof the present invention.

In detail, (a) and (b) of FIG. 3 illustrate a case in which the carrierraster spacing is the same as the bandwidth occupied by one resourceblock as an exemplary embodiment of the method M101.

As illustrated in (a) of FIG. 3, when two adjacent carriers (Carrier 1and Carrier 2) both have an even number (for example, four) of resourceblocks (for example, RB 0, RB 1, RB 2, and RB 3), the method M101 mayperform the carrier allocation as there is no idle band (or band gap)between the carriers (Carrier 1, Carrier 2). This may be applied thesame or a similar way when both of two adjacent carriers have an oddnumber of resource blocks.

However, as illustrated in (b) of FIG. 3, when one carrier (Carrier 1)has an even number (for example, four) of resource blocks (for example,RB 0-RB 3) and the other carrier (Carrier 2) adjacent thereto has an oddnumber (for example, three) of resource blocks (for example, RB 0-RB 2),the idle band (or the band gap) between the carriers (Carrier 1, Carrier2) may be inevitably generated.

To solve the above-described problem, the raster spacing may bedetermined as the multiplication of the subcarrier spacing and N/2, thatis, half of the bandwidth occupied by one resource block. This isreferred to as a method M102. For example, when the subcarrier spacingis 15 kHz and N=12, the raster search spacing may be 90 kHz. Theexemplary embodiment of the method M102 is illustrated in (c) of FIG. 3.

As illustrated in (c) of FIG. 3, when one carrier (Carrier 1) has theeven number (for example, four) of resource blocks (for example, RB 0-RB3) and the other carrier (Carrier 2) has the odd number (for example,three) of resource blocks (for example, RB 0-RB 2), the method M102 mayperform the carrier allocation as there is no idle band (or the bandgap) between the carriers (Carrier 1, Carrier 2).

For the method M101 and the method M102, the center frequency positiondesign is important. If, like the LTE downlink, when one subcarrier ofthe center frequency is defined as the DC (direct current) subcarrierand the DC subcarrier is excluded from the composition of resourceblocks, even if the method M101 or the method M102 is used, the idleband may be inevitably generated between the carriers due to thefrequency part occupied by the DC subcarrier. In contrast, like the LTEuplink, when the center frequency is defined as the middle between twosubcarriers and the resource block is composed by using all subcarriers(however, the subcarrier of a guard band is excluded), theabove-described effect of the method M101 or the method M102 may beobtained. This may also be established for the method described later.

On the other hand, as described above, a plurality of numerologies maybe used in one frequency band. Here, one frequency band may mean aspecific frequency range, and the specific frequency range may be wideor narrow. For example, a specific frequency range may be the bandwidthof one carrier, may be one frequency band having a bandwidth of severalto several hundreds of MHz, or may be a wider region than that.

FIG. 4 is a view showing a case in which a plurality of numerologies areused in a common frequency band. In detail, FIG. 4 illustrates a case inwhich three heterogeneous numerologies (Numerology 1, Numerology 2, andNumerology 3) are used in a common frequency band.

In FIG. 4, it is assumed that the subcarrier spacing of Numerology 2 islarger than the subcarrier spacing of Numerology 1, and the subcarrierspacing of Numerology 3 is larger than the subcarrier spacing ofNumerology 2. This is expressed by the difference between the timedomain of the resource grid lengths (the difference between the OFDMsymbol lengths) or the difference between the frequency domain of theresource grid lengths in FIG. 4. For example, when the subcarrierspacing of Numerology 1 is 15 kHz, the subcarrier spacing of Numerology2 and Numerology 3 may be 30 kHz and 60 kHz, respectively.

A plurality of heterogeneous numerologies may be respectively used forthe different carriers, and may be used together in one carrier. Indetail, FIG. 4 illustrates a case in which Numerology 1 and Numerology 2coexist within one carrier and Numerology 3 constitutes one carrier byitself.

On the other hand, when a plurality of numerologies are used within onefrequency band, the carrier raster may be defined for each numerology.This is referred to as a method M110. In this case, to distinguish thegraduation of the carrier raster for each numerology, an offset of thecarrier raster graduation may be determined. This is referred to as amethod M111.

For example, the carrier raster of Numerology 1 can have a 0 kHz offsetand a 100 kHz spacing, and the carrier raster of Numerology 2 can have a50 kHz offset and a 200 kHz spacing. That is, the frequency such as 100kHz, 200 kHz, 300 kHz, etc. may be the center frequency candidates ofNumerology 1, and the frequency such as 50 kHz, 250 kHz, 450 kHz, etc.may be the center frequency candidates of Numerology 2. In this case,for example, when the terminal initially searches only the cell (or thecarrier) having Numerology 2, the terminal only searches the candidatecenter frequencies having a 50 kHz offset and a 200 kHz spacing. In thiscase, the terminal may assume that Numerology 2 is applied to the entireor some region of the cell (or the carrier) of which the search issuccessful.

Meanwhile, in the case of the method M110, the graduations of thecarrier raster for the numerologies may be defined to have an inclusionrelationship to each other. This is referred to as a method M112.

For example, the carrier raster of Numerology 1 may have a 0 kHz offsetand a 100 kHz spacing, and the carrier raster of Numerology 2 may have a0 kHz offset and a 200 kHz spacing. In this case, the frequency such as100 kHz, 300 kHz, 500 kHz, etc. may be the center frequency candidatesof Numerology 1, and the frequency such as 200 kHz, 400 kHz, 600 kHz,etc. may be the center frequency candidates of Numerology 1 andNumerology 2.

When the terminal initially searches the cell (or the carrier) for theplurality of numerologies within any frequency band, the method M112 mayreduce a number of the carrier raster graduation points to be searchedby the terminal compared with the method M111. In this case, in theillustrations, when the terminal detects the cell in the frequency suchas 200 kHz, 400 kHz, and 600 kHz, a method to distinguish whether thecell detected by the terminal is based on Numerology 1 or Numerology 2is required. This will be described in detail in ‘synchronization signaldesign’ part later.

Meanwhile, in the case of the method M110, the method M111, or themethod M112, the frequency spacing of the carrier raster for thenumerology may be determined to be proportional to the subcarrierspacing of each numerology. This is referred to as a method M113. Forexample, when Numerology 1 and Numerology 2 have the subcarrier spacingof 15 kHz and 30 kHz, the carrier raster spacing of Numerology 2 may betwo times the carrier raster spacing of Numerology 1. In this case, as amethod defining the carrier raster spacing, the method M101 and themethod M102 may be used.

Meanwhile, when N_(RE) as the number of resource elements of oneresource block in the frequency domain is the same for all numerologies,the method M113 may help to minimize the idle band between the carrierswithin the same band.

FIG. 5 is a view showing a carrier raster and a carrier allocation basedon a method M112 or a method M113 according to an exemplary embodimentof the present invention. In detail, in FIG. 5, it is assumed that thesubcarrier spacing of Numerology 2 (N2) is two times the subcarrierspacing of Numerology 1 (N1).

The carrier raster for Numerology 1 (N1) includes the carrier raster forNumerology 2 (N2) by the method M112, and the carrier raster spacing forNumerology 2 (N2) is two times the carrier raster spacing for Numerology1 (N1) by the method M113.

In this case, if it is assumed that N_(RE) (the number of resourceelements of one resource block in the frequency domain) is the same forNumerology 1 (N1) and Numerology 2 (N2), as illustrated in FIG. 5, theresource block of the carrier 2 (Carrier 2) occupies the bandwidth thatis wider than the resource block of the carrier 1 (Carrier 1) by twotimes.

In FIG. 5, it is assumed that the method M101 is used to define theraster spacing. That is, the raster spacing of Numerology 1 (N1) is thesame as the bandwidth occupied by one resource block of the carrier 1,and the raster spacing of Numerology 2 (N2) is the same as the bandwidthoccupied by one resource block of the carrier 2.

As an effect for this, regardless of whether the number of the resourceblocks of the carrier 2 is even (for example, (a) of FIG. 5) or odd (forexample, (b) of FIG. 5), when the carrier 1 has the even number ofresource blocks (RB0-RB3), the carrier allocation may be performed asthere is no idle band (or guard band) between the carriers (Carrier 1,Carrier 2).

If the method M102 is used instead of the method M101, even if thecarrier 1 has the odd number of resource blocks, the carrier allocationmay also be performed as there is no idle band between the carriers.Instead, as the carrier raster spacing is reduced, the cell searchcomplexity may increase.

Meanwhile, one carrier raster may be commonly defined for the pluralityof numerologies. This is referred to as a method M120. For example, thecarrier raster defined with reference to the numerology of the smallestsubcarrier spacing within one frequency band may be used for theplurality of numerologies. In this case, because the terminal may needto perform the cell search for the plurality of numerologies for allcarrier raster graduation points, the method M120 may increase thecomplexity compared with the method M112.

Meanwhile, the carrier raster may be defined for each frequency band.For example, it may be defined so that only numerology(ies) having thesubcarrier spacing that is relatively large is used in the highfrequency band. In this case, the carrier raster for the high frequencyband may have the wider spacing than that of the carrier raster for thelow frequency band.

[Synchronization Signal]

According to the above description, the terminal may need to assume theplurality of numerologies for one carrier raster graduation and thesynchronization signal or the cell (or the carrier) thereof in theinitial cell search process.

Hereinafter, a method of transmitting the synchronization signal for theinitial cell search of the terminal through the base station in the casein which the plurality of numerologies are used within the commonfrequency range will be described.

Firstly, a case of the carrier configured of the single numerology isconsidered. In this case, the method M200 and the method M210 existaccording to the relationship between the numerology of thesynchronization signal and the numerology of the carrier.

The method M200 is a method in which the numerology applied to thesynchronization signal follows the numerology of the carrier to whichthe synchronization signal belongs.

According to the method M200, because there is no interference betweenthe synchronization signal and the signal of the adjacent frequencydomain, the method M200 has a merit that it is not necessary toadditionally set the guard band.

The terminal may attempt the detection of the synchronization signal byeach numerology for the plurality of numerologies candidates. When theterminal has the successfully detected synchronization signal, theterminal may consider the numerology of the detected synchronizationsignal as the numerology of the carrier to which the detectedsynchronization signal belongs.

When the synchronization signal detection is performed in the timedomain, the process thereof may be performed through the sampling, thefiltering, and a correlator. Here, the filtering may be low-passfiltering when the synchronization signal is disposed to be symmetricwith reference of the center frequency like the LTE. The correlator maybe implemented with an auto-correlator, a self-correlator, or across-correlator according to the characteristic of the synchronizationsignal sequence.

As a sequence of the synchronization signal, a Zadoff-Chu sequence, aGold sequence, and the like may be used. When the resource region of thesynchronization signal is configured with a plurality of OFDM symbols,the sequence of the synchronization signal may be defined for each OFDMsymbol and may be a long sequence occupying the plurality of OFDMsymbols.

Hereinafter, the method M201 and the method M202 will be described asdetailed methods of the method M200.

The method M201 is the method in which the time-frequency resourceelement configuration of the synchronization signal resource region isthe same for the plurality of numerologies. That is, the method M201 isthe method in which the resource element mapping of the synchronizationsignal is the same regardless of the numerology.

FIG. 6 is a view showing a synchronization signal resource region basedon a method M201 according to an exemplary embodiment of the presentinvention.

In detail, FIG. 6 illustrates a case in which the method M201 is appliedto two numerologies (Numerology 1 and Numerology 2) that are differentfrom each other. In FIG. 6, it is assumed that the sequence length ofthe synchronization signal is 6 and the subcarrier spacing of Numerology2 is larger than the subcarrier spacing of Numerology 1.

According to the method M201, for both of Numerology 1 and Numerology 2,the resource region of the synchronization signal occupies one resourceelement (i.e., one OFDM symbol) in the time domain and occupies sixcontinuous resource elements in the frequency domain.

F_(BW,1) represents the bandwidth occupied by the synchronization signalapplied with Numerology 1, and F_(BW,2) represents the bandwidthoccupied by the synchronization signal applied with Numerology 2.F_(BW,2) is larger than F_(BW,1).

In the case in which the method M201 is used, because the terminal needsto apply the different sampling, the different filtering, and/or thedifferent correlator for each numerology, the complexity and the delaytime for the initial cell search of the terminal may increase. Also,when the subcarrier spacing of the numerology is large, because thebandwidth used to the initial cell search increases, a required samplingrate may increase. For example, when the subcarrier spacing of thecarrier is 60 kHz, the high sampling rate of four times may be requiredcompared with the case in which the subcarrier spacing is 15 kHz. Incontrast, since the period in which the synchronization signal istransmitted decreases as the subcarrier spacing increase, the methodM201 may be advantageous to beam sweeping-based transmission in the highfrequency band.

In the present specification, the resource region of the synchronizationsignal basically means a group of the resource elements in which thesynchronization signal is mapped. Meanwhile, when the band passfiltering for the synchronization signal detection of the terminal isnon-ideal, the guard band may need to be inserted at both ends of thebandwidth of the synchronization signal. For example, in the LTE, fiveadjacent subcarriers existing at both ends of the bandwidth of the PSSand the SSS are defined as the guard band. In this case, the resourceregion of the synchronization signal may mean the region including boththe resource region where the synchronization signal is mapped and theguard band.

The method M202 is a method defining the bandwidth so that the bandwidthoccupied by the synchronization signal resource region is the same orsimilar regardless of the numerology.

FIG. 7 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal based on a method M202according to an exemplary embodiment of the present invention.

In detail, FIG. 7 illustrates a case in which the method M202 is appliedto two different numerologies (Numerology 1 and Numerology 2). In FIG.7, it is assumed that the subcarrier spacing (2*K) for Numerology 2 istwo times the subcarrier spacing (K) for Numerology 1. That is, in FIG.7, it is assumed that the OFDM symbol length L for Numerology 1 is twotimes the OFDM symbol length L/2 for Numerology 2.

In FIG. 7, it is assumed that the number of resource elementsconstituting the resource region of the synchronization signal is 8 inthe case of Numerology 1 and 12 in the case of Numerology 2.

According to the method M202, the resource region of the synchronizationsignal includes eight resource elements in the frequency domain and oneresource element in the time domain in the case of Numerology 1, andincludes four resource elements in the frequency domain and threeresource elements in the time domain in the case of Numerology 2. Inthis case, F_(BW,1) and F_(BW,2) of the bandwidth of the synchronizationsignal resource region are the same (i.e., F_(BW,1)=F_(BW,2)=F).Accordingly, the method M202 has the merit that the terminal may applythe same filtering to the plurality of numerologies in the initial cellsearch process. Also, the method M202 may transmit the synchronizationsignal to the narrow bandwidth regardless of the subcarrier spacing ofthe numerology. In contrast, in the method M202, since the number of theOFDM symbols occupied by the synchronization signal resource region maybe different for each numerology, the sequence design considering thisand the coexistence design with the other signals and channelsconsidering this are required.

In the method M202, the fact that the bandwidths of the synchronizationsignal resource region are similar regardless of the numerologies maymean that the bandwidths are sufficiently similar (for example, within afew subcarriers difference) in applying the common filtering to theplurality of numerologies through the terminal.

Meanwhile, in the method M202, a method for performing the mapping maybe considered so that the time duration is also the same or similarregardless of the numerology as well as the bandwidth of thesynchronization signal resource region. This is referred to as a methodM203.

FIG. 8 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal based on a method M203according to an exemplary embodiment of the present invention.

In detail, in FIG. 8, like the exemplary embodiment of FIG. 7, it isassumed that the subcarrier spacing (2*K) for Numerology 2 is two timesthe subcarrier spacing (K) for Numerology 1. That is, in FIG. 8, it isassumed that the OFDM symbol length L for Numerology 1 is two times theOFDM symbol length L/2 for Numerology 2.

In FIG. 8, it is assumed that the number of resource elementsconstituting the synchronization signal resource region is 8 in both thecase of Numerology 1 and the case of Numerology 2.

According to the method M203, the resource region of the synchronizationsignal includes eight resource elements in the frequency domain and oneresource element in the time domain in the case of Numerology 1, andincludes four resource elements in the frequency domain and two resourceelements in the time domain in the case of Numerology 2. That is, thebandwidth F_(BW,1) occupied by the synchronization signal resourceregion for Numerology 1 and the bandwidth F_(BW,2) occupied by thesynchronization signal resource region for Numerology 2 are the same,and the time duration T occupied by the synchronization signal resourceregion for Numerology 1 and the time duration T occupied by thesynchronization signal resource region for Numerology 2 are the same.

Also, in the method M202 or the method M203, the frequency resourceregion may be the same for the plurality of numerologies as well as thefrequency bandwidth of the synchronization signal resource region. Forexample, the synchronization signal may occupy the bandwidth of F_(BW,1)Hz or F_(BW,2) Hz at the center of the system bandwidth regardless ofthe numerology.

The method M210 is a method in which the numerology applied to thesynchronization signal is fixed regardless of the numerology of thecarrier to which the synchronization signal belongs.

FIG. 9 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal based on a method M210according to an exemplary embodiment of the present invention.

In detail, FIG. 9 illustrates a case in which the synchronization signalof the carrier applied with Numerology 1 and the synchronization signalof the carrier applied with Numerology 2 both follow Numerology 1. Forexample, in the case of Numerology 1, the resource region for thesynchronization signal includes eight resource elements in the frequencydomain and one resource element in the time domain. That is, thebandwidth F and the time duration T occupied by the synchronizationsignal resource region for Numerology 1 are the same as the bandwidth Fand the time duration T occupied by the synchronization signal resourceregion for Numerology 2.

In FIG. 9, it is assumed that the subcarrier spacing (2*K) forNumerology 2 is two times the subcarrier spacing (K) for Numerology 1.That is, in FIG. 9, it is assumed that the OFDM symbol length L forNumerology 1 is two times the OFDM symbol length L/2 for Numerology 2.

The method M210 may be applied within a specific frequency range.

The method M210 may predetermine the numerology for the synchronizationsignal as one among the numerologies allowed within a specific frequencyrange. For example, the synchronization signal in the frequency band of6 GHz or less may always be transmitted based on the numerology havingthe subcarrier spacing of 15 kHz.

According to the method M210, the terminal may search thesynchronization signal through a single numerology in the initial cellsearch process.

However, since the numerology of the synchronization signal and thenumerology of the carrier may be different, a separate method that iscapable of determining which numerology the terminal applies to thecarrier is required. The terminal may explicitly or implicitly acquirethe numerology of the carrier through the synchronization signalreception. Also, the terminal may obtain the numerology of the carrierthrough the signal or the channel (for example, PBCH) received by theterminal after the synchronization signal. In this case, the signal orthe channel received by the terminal after the synchronization signalfollows the same numerology as the numerology of the synchronizationsignal. In the method M210, since the numerology of the signal and thechannel adjacent to the synchronization signal in the frequency domainmay be different from the numerology of the synchronization signal, anadditional guard band may be inserted to both ends of the bandwidth ofthe synchronization signal.

Next, a case of the carrier configured with a plurality of numerologiesis considered.

In one carrier, the plurality of numerologies may be multiplexed throughthe TDM (time division multiplexing), or may be multiplexed through theFDM (frequency division multiplexing) like the exemplary embodiment ofFIG. 4. In this case, a method (hereinafter, ‘method M220’) in which aplurality of numerologies share one synchronization signal and a method(hereinafter, ‘method M230’) in which the synchronization signal istransmitted for each numerology may be used.

In the case in which the plurality of numerologies share onesynchronization signal, like the method M200, the numerology of thesynchronization signal may follow one among the plurality ofnumerologies within the carrier. This is referred to as a method M221.The method M221 will be described with reference to FIG. 10.

FIG. 10 is a view showing a numerology of a synchronization signal and aresource region of a synchronization signal for a carrier composed of aplurality of numerologies according to an exemplary embodiment of thepresent invention.

FIG. 10 illustrates a case in which two numerologies (Numerology 1,Numerology 2) are applied in one carrier.

In FIG. 10, it is assumed that the subcarrier spacing for Numerology 2is larger than the subcarrier spacing for Numerology 1. That is, in FIG.10, it is assumed that the OFDM symbol length for Numerology 1 is largerthan the OFDM symbol length for Numerology 2.

As illustrated in FIG. 10, the synchronization signal resource regionmay be defined within the resource region to which the same numerologyas the numerology (for example, Numerology 1) of the synchronizationsignal is applied. FIG. 10 illustrates the case in which the resourceregion for the synchronization signal includes six resource elements inthe frequency domain and one resource element in the time domain.

The numerology of the synchronization signal may be used as the basenumerology within one carrier. That is, the terminal accessed to thecorresponding carrier may receive the signal by using the basenumerology within the specific time-frequency resource region beforeseparately configured with a numerology.

When only one synchronization signal exists in the carrier consisting ofthe plurality of numerologies, the synchronization signal may be definedat the center of the carrier bandwidth (for example, to be symmetricalbased on the center frequency). In this case, when the plurality ofnumerologies are multiplexed through the FDM, the terminal may at leastassume the same numerology as the numerology of the synchronizationsignal for the center bandwidth occupied with the synchronizationsignal.

As the resource region configuration method of the synchronizationsignal, the above-described methods (for example, the method M201, themethod M202, the method M203, etc.) may be used.

Meanwhile, when the plurality of numerologies share one synchronizationsignal, like the method M210, the numerology of the synchronizationsignal may follow a predetermined numerology regardless of thenumerologies of the carrier. This is referred to as a method M222.

When the synchronization signal is transmitted for each numerologywithin one carrier, the numerology of each synchronization signal mayfollow the numerology of the resource region in which thesynchronization signal is defined. This is referred to as a method M231.The method M231 may be considered as the method M200 being appliedwithin one carrier.

In this case, the configuration of the synchronization signal resourceregion may follow the above-described method (for example, the methodM201, the method M202, the method M203, etc.).

Differently from the method M231, the numerology of all synchronizationsignals within one carrier may follow one among a plurality ofnumerologies constituting the carrier. This is referred to as a methodM232.

Also, the numerology of all synchronization signals within one carriermay follow a predetermined numerology regardless of the numerology ofthe carrier. This is referred to as a method M233.

When the above-described methods are applied to a carrier consisting ofa plurality of numerologies, a capability of the terminal may beconsidered.

When a NR terminal is basically capable of receiving a plurality ofnumerologies, the method M220 may be used. A terminal supporting theeMBB and the URLLC may correspond to this. In this case, the terminalmay use the different numerologies from each other for thesynchronization signal reception and the data reception.

In contrast, for the terminal without the capability of receiving theplurality of numerologies, the method M230 may be used. A low-costterminal to support only a specific numerology for the mMTC transmissionmay correspond to this. In this case, the terminal uses the samenumerology for the synchronization signal reception and the datareception.

Within one carrier, the method M220 and the method M230 may be combinedand used.

In the above-described methods (for example, the method M200 to themethod M233), transmission timing and the periodicity of thesynchronization signal may be the same for a plurality of numerologies.

Meanwhile, since the length of the subframe and the group of thesubframe numbers may be different from each other for the heterogeneousframe structure having the different numerologies, the transmissiontiming and the periodicity of the synchronization signal may beexpressed by different equations for each frame structure.

When the transmission timing and the periodicity of the synchronizationsignal are the same, the initial cell search complexity of the terminalmay be reduced.

Meanwhile, in the above-described methods, the different signals (or thedifferent channels) may be mapped to the resource region of thesynchronization signal. That is, within the synchronization signalresource region, the synchronization signal and the signal (or thechannel) other than the synchronization signal may coexist. For example,when the synchronization signal is mapped to the non-continuous resourceelements in the frequency domain, the resource elements to which thesynchronization signal is not mapped may be used for the transmission ofthe other signals (or the channels).

The above-described synchronization signal may be limited to the usagesearching the center frequency of the cell (or the carrier) in theinitial cell search process of the terminal. In this case, in thefrequency domain that does not support a standalone operation of thecell (or the carrier), the synchronization signal may not exist. Also,when the cell (or the carrier) is operated as an only secondary cell,the synchronization signal may not exist.

Meanwhile, the above-described synchronization signal may also be usedfor synchronization acquisition, synchronization tracking, and/or cellID acquisition of the terminal as well as the center frequency search.

Also, the above-described synchronization signal may be used as a pilotfor the channel estimation (or the data decoding).

Particularly, when the synchronization signal is used for other uses aswell as the center frequency search, the synchronization signal may beconfigured with a plurality of synchronization signals. For example, thesynchronization signal may be configured with a first synchronizationsignal and a second synchronization signal. When the synchronizationsignal is configured with a plurality of synchronization signals, theabove-described methods (for example, the method M200 to the methodM210) may only be applied to some of synchronization signals (forexample, the first synchronization signal). Also, the above-describedmethods (for example, the method M200 to the method M210) may be appliedto the plurality of synchronization signals (for example, the firstsynchronization signal, the second synchronization signal). In thiscase, the synchronization signal resource region defined for theabove-described methods (for example, the method M200 to the methodM210) may include only some of synchronization signals in the formercase and may include the plurality of synchronization signals in thelatter case.

[Signal Composition for Initial Access]

Since the NR supports the wide range of frequency, the operation of thehigh frequency band and the operation of the low frequency band may bedifferent from each other.

In the high frequency band in which a path loss of the signal is large,transmit beamforming and/or receive beamforming may be applied. For acoverage extension of the cell or the terminal, a beamforming may alsobe applied to the common signal and the control channel as well as thedata channel. In this case, when a beam having a small beamwidth isformed through a plurality of antennas, to cover the entire coverage ofthe cell or the sector, the signal may need to be received ortransmitted several times through the beams having a plurality ofdifferent direction directivities. To transmit the signal applied withthe beamforming through the different resources from each other in thetime domain is referred to as beam sweeping.

In contrast, in the low frequency band in which the path loss of thesignal is relatively small, even if the common signal and the controlchannel are transmitted one time, the entire coverage of the cell or thesector may be covered.

The initial access procedure of the NR must support all theabove-different beam operations.

Hereinafter, the resource composition and the transmission method forthe signals for the initial access of the terminal will be described. Amethod (a band-agnostic or beam operation-agnostic method) that may becommonly used regardless of the frequency band or the beam operationwill be described.

For the initial access of the terminal, a downlink discovery signal andan uplink PRACH may be used.

First, the downlink discovery signal will be described.

The discovery signal may be the downlink signal for the cell search,system information acquisition, beam acquisition and tracking, and so onof the terminal, and may be periodically transmitted to the terminal. Adiscovery signal occasion may be defined.

FIG. 11 is a view showing a constituent element of a discovery signalaccording to an exemplary embodiment of the present invention.

The discovery signal occasion may consist of the synchronization signaland the PBCH, as illustrated in (a) of FIG. 11.

The synchronization signal may be used for the time-frequencysynchronization, the cell ID acquisition, etc., and the PBCH may be usedto transmit system information (SI) that is essential for the initialaccess. A cell (or a base station) that does not support the initialaccess may not transmit the PBCH. That is, the discovery signal occasionmay not include the PBCH.

The synchronization signal may be composed of a plurality ofsynchronization signals. For example, the synchronization signal mayconsist of a primary synchronization signal (PSS) and a secondarysynchronization signal (SSS).

Also, as illustrated in (b) of FIG. 11 or (c) of FIG. 11, the discoverysignal occasion may consist of the synchronization signal, PBCH, and abeam reference signal (BRS).

The BRS may be used for beam or beam ID acquisition, RRM (radio resourcemanagement) measurement, and/or PBCH decoding. The TDM may be appliedbetween the PBCH and the BRS. Also, for better PBCH decodingperformance, as illustrated in (c) of FIG. 11, the PBCH and the BRS maycoexist in a common region.

Also, the discovery signal occasion may include the reference signal forCSI (channel state information) measurement and reporting, that is, aCSI-RS (reference signal). The discovery signal occasion may alsoinclude a separate reference signal for the beam tracking. The CSI-RSand/or the beam tracking reference signal may be set to be terminalspecific (UE-specific).

When the discovery signal occasion is used for the initial cell searchof the terminal, a transmission periodicity and an offset of thediscovery signal occasion may be a fixed value that is predefined.

It is assumed that M time-frequency resources exist for each of thesynchronization signal, the PBCH, and/or the BRS within one discoverysignal occasion periodicity. Here, M is a natural number. That is, theelement signals included in the discovery signal occasion mayrespectively use the M resources. The M resources for each elementsignal have the same bandwidth and the same time duration (for example,the same number of OFDM symbols).

In a case of M>1, the beam sweeping may be applied to each of thesynchronization signal, the PBCH, and/or the BRS through the pluralityof resources. In a case of M=1, a single beam may be transmitted or aplurality of beams may be transmitted through SDM (spatial divisionmultiplexing) on the same resource.

The discovery signal occasion may consist of a plurality of signalblocks. The resource occupied by one signal block is continuous in thetime and frequency domains. That is, the resource occupied by one signalblock may include time domain symbols that are continuous in the timedomain. In this case, a method M300 and a method M310 may be consideredaccording to the element signal constituting the signal blocks.

The method M300 is a method in which the discovery signal occasionconsists of the heterogeneous signal blocks. That is, the discoverysignal occasion may consist of the synchronization signal block(s) andthe PBCH block. In this case, when the BRS exists for the decoding ofthe PBCH, the BRS may be included in the PBCH block.

FIG. 12 is a view showing a resource configuration of a discovery signaloccasion based on a method M300 according to an exemplary embodiment ofthe present invention.

In detail, FIG. 12 illustrates a case in which the discovery signaloccasion consists of three heterogeneous signal blocks (a first signalblock, a second signal block, and a third signal block).

The first signal block is the PSS block, and includes M PSS resourcesclassified through the TDM. The second signal block is the SSS block andincludes M SSS resources classified through the TDM. The third signalblock is the PBCH block and includes M PBCH resources and/or M BRSresources classified through the TDM.

As another example, the discovery signal occasion may be configured oftwo heterogeneous signal blocks (a first signal block and a secondsignal block). The first signal block is the PSS and the SSS block andincludes the M PSS resources and the M SSS resources classified throughthe TDM. The second signal block is the PBCH block and includes the MPBCH resources and/or the M BRS resources classified through the TDM. Inthis case, the PSS resources and the SSS resources may be arranged to becrossed in the order of {PSS #0, SSS #0, PSS #1, SSS #1, . . . , PSS #M−1, SSS # M−1} in the time domain within the first signal block.

The method M310 is a method in which the discovery signal occasionconsists of the homogeneous signal block(s), that is, the discoverysignal block(s). The method M310 will be described with reference toFIG. 13.

FIG. 13 is a view showing a resource composition of a discovery signaloccasion based on a method M310 according to an exemplary embodiment ofthe present invention. In FIG. 13 to FIG. 18, DS means the discoverysignal.

The discovery signal occasion consists of the M discovery signalblock(s), and one discovery signal block includes one synchronizationsignal resource, one PBCH resource, and/or one BRS resource.

FIG. 13 illustrates a case in which the synchronization signal consistsof the PSS and the SSS and the TDM is applied between the PSS resource,the SSS resource, and the PBCH resource within each discovery signalblock. One synchronization signal resource included in one discoverysignal block is classified into the PSS resource and the SSS resource.

When the terminal firstly receives the PSS and then receives the SSSnext, it is advantageous that the PSS is transmitted earlier than theSSS in time within one discovery signal block.

Meanwhile, in the method M300 and the method M310, the TDM and/or theFDM may be applied between the signal blocks.

FIG. 14 is a view showing a case in which a TDM is applied betweensignal blocks in a method M300 or a method M310 according to anexemplary embodiment of the present invention.

When the discovery signal occasion occupies only one sub-band, the TDMmay be applied between the signal blocks. This case is illustrated in(a) of FIG. 14, (b) of FIG. 14, and (c) of FIG. 14. When the discoverysignal occasion occupies the plurality of sub-bands, both the TDM andthe FDM may be applied among the signal blocks.

(a) of FIG. 14 and (b) of FIG. 14 represent an exemplary embodiment ofthe method M300, and (c) of FIG. 14 represents an exemplary embodimentof the method M310.

In (a) of FIG. 14, a time distance between the PSS block (including theM PSS resources) and the SSS block (including the M SSS resources) isT_(B,0), and the time distance between the SSS block and the PBCH block(including the M PBCH resources and/or the M BRS resources) is T_(B,1).

In (b) of FIG. 14, the time distance between the PSS/SSS block(including the M PSS resources and the M SSS resources) and the PBCHblock (including the M PBCH resources and/or the M BRS resources) isT_(B).

In (c) of FIG. 14, the time distance between the M discovery signalblocks is T_(S,0), T_(S,1), . . . , T_(S,(M-2)). Each discovery signalblock includes one synchronization signal resource (the PSS resource,the SSS resource), one PBCH resource, and/or one BRS resource.

The bandwidth(s) of the sub-bands occupied by one discovery signaloccasion may all be the same. This bandwidth is referred to as cellsearch bandwidth.

When the guard band is inserted at both ends of the bandwidth of thesynchronization signal, the synchronization signal bandwidth includingthe guard band may be the same as the PBCH bandwidth.

The method M310 has some merits compared with the method M300.

First, because the channel variation is relatively small within onediscovery signal block, when the antenna port of the PSS/SSS and theantenna port of the PBCH are the same, the PSS/SSS may help the decodingof the PBCH or the BRS-based RRM measurement.

Secondly, because the method M300 must perform the beam sweeping foreach signal block in the case of M>1, fast beamforming change isrequired. However, because the method M310 may change the beamformingacross the discovery signal blocks and may apply the same or similarbeam within a discovery signal block, the beamforming change may lessfrequently occur.

Finally, according to the method M300, a relative distance (for example,the time domain distance and the frequency domain distance) among them-th PSS resource, the m-th SSS resource, and the m-th PBCH resource maybe changed depending on a beamforming mode, that is, the value of M.Here, m is a resource index and is an integer greater than or equal to 0and less than or equal to M−1. Accordingly, after the terminal receivesthe PSS, resource position information of the SSS or the PBCH may needto be provided from the base station to receive the SSS or the PBCH. Forexample, the terminal may also need to obtain the value of M through thePSS reception to know the resource position of the SSS or the PBCH.

In contrast, according to the method M310, the relative distance (forexample, the time domain distance and the frequency domain distance)between the m-th PSS resource, the m-th SSS resource, and the m-th PBCHresource is constant regardless of the value of M. In the presentspecification, the frequency domain distance between the resources meansthe relative distance between the frequency regions occupied by theresources. This may be applied to a case in which the frequencyresources overlap with each other in the frequency domain. For example,the time and the frequency distances between the PSS (or the PSSresource) and the SSS (or the SSS resource) included in the m-thdiscovery signal block generated by the base station are the same as thetime and frequency distances between the PSS (or the PSS resource) andthe SSS (or the SSS resource) included in the (m+1)-th discovery signalblock generated in the base station. That is, the time domain distancebetween the PSS resource and the SSS resource included in the m-thdiscovery signal block is the same as the time domain distance betweenthe PSS resource and the SSS resource included in the (m+1)-th discoverysignal block, and the frequency domain distance between the PSS resourceand the SSS resource included in the m-th discovery signal block is thesame as the frequency domain distance between the PSS resource and theSSS resource included in the (m+1)-th discovery signal block. Likewise,the time and frequency distances between the SSS (or the SSS resource)and the PBCH (or the PBCH resource) included in the m-th discoverysignal block are the same as the time and frequency distances betweenthe SSS (or the SSS resource) and the PBCH (or the PBCH resource)included in the (m+1)-th discovery signal block. Likewise, the time andfrequency distances between the PSS (or the PSS resource) and the PBCH(or the PBCH resource) included in the m-th discovery signal block arethe same as the time and frequency distances between the PSS (or the PSSresource) and the PBCH (or the PBCH resource) included in the (m+1)-thdiscovery signal block.

Accordingly, after detecting the PSS, the terminal may receive the SSSor the PBCH at the position determined within the discovery signal block(for example, the m-th discovery signal block) including the PSSresource (for example, the m-th PSS resource) in which the PSS isdetected. That is, the terminal does not need to know the resource ofall signal blocks constituting the discovery signal occasion, and it issufficient to assume that one discovery signal block including the PSSresource of which the PSS is detected is transmitted. Therefore,according to the method M310, the terminal does not need to know thebeamforming mode, that is, the value of M in the discovery signalreceiving process for the initial cell search.

Meanwhile, the terminal may assume (or determine) a discovery signalmeasurement window (DMW) to receive the discovery signal occasion.

FIG. 15 is a view showing a case in which a discovery signal occasion istransmitted in a discovery signal measurement window according to anexemplary embodiment of the present invention.

In FIG. 15, it is assumed that the TDM is applied between the Mdiscovery signal blocks.

The terminal may monitor, find, and measure the discovery signal withinthe discovery signal measurement window.

When the method M310 is applied to the resource composition of thediscovery signal occasion and the PSS, the SSS, and the PBCH as theelement signal are included in the discovery signal occasion, theterminal may monitor the PSS within the discovery signal measurementwindow.

In this case, the terminal may find one or more PSS beam transmittedfrom the same cell. When the terminal finds at least one PSScorresponding to at least one discovery signal block within thediscovery signal measurement window, one among at least one PSS may beselected.

To select one among at least one found PSS beam, after the terminalmonitors the entire time duration of the discovery signal measurementwindow, a method (hereinafter, ‘a first selection method’) of selectingthe PSS beam (or the PSS resource corresponding to the PSS beam) ofwhich the reception performance is the best among the found PSS beam(s)may be used. Also, to select one among at least one found PSS beam, amethod (hereinafter, ‘a second selection method’) performing themonitoring until the terminal finds one PSS beam (or the PSS resourcecorresponding to the PSS beam) satisfying a predetermined receptionperformance condition may be used. The first selection method provideshigher reception performance compared with the second selection method,however discovery signal receiving complexity of the terminal mayincrease.

Also, the terminal may monitor the SSS or the PBCH at the positiondetermined within the discovery signal block (for example, the m-thdiscovery signal block) corresponding to the PSS (for example, the PSShaving the best reception performance or satisfying the predefinedreception performance condition) selected by the first selection methodor the second selection method.

On the other hand, FIG. 15 illustrates a case in which the discoverysignal measurement window is continuously predetermined in thetime-frequency domain within one DMW periodicity.

However, the discovery signal measurement window may also bediscontinuous in the time or frequency domain. That is, a plurality ofresource blocks may constitute the discovery signal measurement windowin the time domain or the frequency domain within one discovery signalmeasurement window periodicity. In this case, each resource block maymean a group of the continuous resources in the time domain and thefrequency domain, and the resource blocks may not be adjacent in thetime domain and/or the frequency domain.

The terminal that is not connected by RRC (radio resource control) mayassume the discovery signal measurement window information (for example,a DMW duration and a DMW periodicity) as a predetermined value. That is,the terminal that is not connected to the base station by the RRC maydetermine the duration and the periodicity for the discovery signalmeasurement window based on the predefined duration value andperiodicity value. For example, the discovery signal measurement windowperiodicity for the terminal attempting the initial access may bedefined as 5 ms like the LTE, and the discovery signal measurementwindow duration for the terminal may be defined as a fixed value of lessthan 5 ms. When the duration and the periodicity of the discovery signalmeasurement window are the same, the terminal that is not connected bythe RRC may monitor the discovery signal in the whole time instances.

Meanwhile, the RRC-connected terminal (or the terminal that is notconnected by the RRC but may be able to receive system information fromthe base station) may receive the configuration of the discovery signalmeasurement window information (for example, the DMW duration and theDMW periodicity) from the base station. In this case, to decrease thereceiving complexity of the terminal, the discovery signal measurementwindow periodicity may be set to be longer than the value assumed by theterminal that is not connected by the RRC, and the discovery signalmeasurement window duration may be set to be shorter than the valueassumed by the terminal that is not connected by the RRC. For example,the periodicity and the duration of the discovery signal measurementwindow may be set as 40 ms and 2 ms, respectively. That is, the basestation may set the DMW periodicity for the terminal that is connectedto the base station by the RRC as the value that is larger than theperiodicity value that is predetermined for the terminal that is notconnected to the base station by the RRC. Also, the base station may setthe DMW duration for the terminal that is connected to the base stationby the RRC as the value that is smaller than the duration value that ispredetermined for the terminal that is not connected to the base stationby the RRC.

When the RRC-connected terminal does not receive the configuration ofthe discovery signal measurement window information (for example, theDMW duration and the DMW periodicity) from the base station, theRRC-connected terminal may not perform the discovery signal measurement.That is, the discovery signal measurement window information (forexample, the DMW duration and the DMW periodicity) may be set to theterminal only when the terminal discovery signal measurement isnecessary. Also, in this case, the RRC-connected terminal may assume thediscovery signal measurement window information (for example, the DMWduration and the DMW periodicity) as the same value as the value assumedby the terminal that is not connected by the RRC.

The discovery signal measurement window information (for example, theDMW duration and the DMW periodicity) may be signaled as terminalspecific (UE-specific).

FIG. 15 illustrates a case in which all signals (for example, the Mdiscovery signal blocks) constituting the discovery signal occasion aretransmitted by the base station within the discovery signal measurementwindow. In contrast, in the terminal specific discovery signalmeasurement window, only a part (for example, one or a plurality ofdiscovery signal blocks) of the signals constituting the discoverysignal occasion may be transmitted. Also, within the discovery signalmeasurement window, no signal constituting the discovery signal occasionmay be transmitted.

Meanwhile, a resource pool (hereinafter, ‘a discovery signal resourcepool’) to transmit the discovery signal occasion may be defined. Thatis, the discovery signal occasion may be transmitted within a predefineddiscovery signal resource pool. In this case, the periodicity of thediscovery signal occasion may not be separately defined, and theperiodicity of the discovery signal resource pool may be vicariouslydefined.

The base station may allocate a part or all of the resources belongingto the discovery signal resource pool predefined for the transmission ofthe discovery signal to at least one discovery signal block. FIG. 15illustrates a case in which the base station allocates a part of theresources belonging to the discovery signal resource pool to the Mdiscovery signal blocks constituting the discovery signal occasion.

FIG. 15 illustrates a case in which the region of the discovery signalresource pool is identical to the region of the discovery signalmeasurement window. However, the region of the discovery signal resourcepool and the region of the discovery signal measurement window may notbe identical.

Hereinafter, the relationship between the discovery signal and the PRACHwill be described.

In the NR system, like the LTE, the PRACH may be used for the randomaccess of the terminal or the terminal discovery of the base station.

The terminal may transmit the preamble or encoded signal through thePRACH. In detail, the operation related to the PRACH resourceconfiguration method for the case using the method M310 will bedescribed. For this, the PRACH occasion may be defined.

Like the composition of the discovery signal occasion with the Mdiscovery signal blocks in the method M310, the PRACH occasion may becomposed of M PRACH blocks (or PRACH resources) (only m=0, 1, . . . ,M−1) within one PRACH occasion periodicity for the receive beamformingof the base station. The resources occupied by one PRACH block arecontinuous in the time-frequency domain.

FIG. 16 is a view showing a discovery signal and a PRACH resourcecomposition based on a method M310 according to an exemplary embodimentof the present invention.

In detail, FIG. 16, as an exemplary embodiment of the resourcecomposition of the PRACH occasion, the M discovery signal blocks and theM PRACH blocks for the PRACH reception of the base station exist withinone cell search bandwidth.

In FIG. 16, T_(S,m) (for example, T_(S,0), T_(S,1), . . . , T_(S,(M-2)))represents the time domain distance between the m-th discovery signalblock and the (m+1)-th discovery signal block, T_(R,m) (for example,T_(R,0), T_(R,1), . . . , T_(R,(M-2))) represents the time domaindistance between the m-th PRACH block and the (m+1)-th PRACH block, andT_(G,m) (for example, T_(G,0), T_(G,1), . . . , T_(G,(M-1))) representsthe time domain distance between the m-th discovery signal block and them-th PRACH block. However, the exemplary embodiment of FIG. 16 is onlyone example, and a case in which the signal blocks are mapped to thedifferent frequency resources from each other may be considered.

The base station attempts the PRACH reception in all M PRACH blocks. Inthis case, the base station may derive the receiving beam for the m-thPRACH block among the M PRACH block based on the transmission beam forthe m-th discovery signal block among the M discovery signal blocks.When reciprocity is established between the uplink channel and thedownlink channel like the TDD, the transmission beam and the receivingbeam may be the same or similar.

When the terminal succeeds in the detection of the synchronizationsignal and/or the BRS in the m-th discovery signal block, the terminaltransmits the preamble in the m-th PRACH block. This terminal operationis referred to as a method M311. If the terminal also performs thebeamforming, like the base station, the terminal may derive thetransmission beam of the m-th PRACH block based on the receiving beam ofthe m-th discovery signal block. According to the method M310 and themethod M311, the terminal only needs to know the resource position ofthe m-th PRACH block among the M PRACH blocks.

The resource position of the m-th PRACH block may be expressed by a timeoffset and a frequency offset from the resource of the m-th discoverysignal block. In the exemplary embodiment of FIG. 16, because thefrequency offset is 0, the resource position of the m-th PRACH block maybe expressed by only the time offset T_(G,m).

In this case, the time offset {T_(G,m)} may be defined to have the samevalue T_(G) for all m (where m=0, 1, . . . , M−1). This is referred toas a method M320. In contrast, the time offset {T_(G,m)} may be allowedto have different values according to m. This is referred to as a methodM321.

In the case of the method M320, the value of T_(G) may be predefined inthe technical specification or may be transmitted to the terminal by thediscovery signal. In the case of the method M321, the value of T_(G,m)may be transmitted to the terminal by the m-th discovery signal block.Although the method M321 has a burden of informing the resourceconfiguration information of the PRACH block to the terminal, the methodM321 has high flexibility of resource configuration compared with themethod M320.

When the frequency offset exists between the PRACH block and thediscovery signal block, the above-described methods may also besimilarly applied to the frequency offset.

Meanwhile, {T_(S,m)} and {T_(R,m)} may be previously defined in thetechnical specification. This is referred to as a method M330. Forexample, T_(S,0)=T_(S,1)= . . . =T_(S,(M-2))=T_(S), T_(R,0)=T_(R,1)= . .. =T_(R,(M-2))=T_(R), and T_(S), and T_(R) may have the fixed values. Asthe values of T_(S) and T_(R) decrease, the time required for the beamsweeping may decrease. That is, the time distance between the m-thdiscovery signal block and the (m+1)-th discovery signal block isdetermined based on the predefined T_(S) value, and the time distancebetween the m-th PRACH block and the (m+1)-th PRACH block is determinedbased on the predefined T_(R) value.

FIG. 17 is a view showing a discovery signal and a PRACH resourcecomposition based on a method M320 and a method M330 according to anexemplary embodiment of the present invention.

FIG. 17 illustrates a case of (T_(S), T_(R))=(0, 0) as the exemplaryembodiment of the method M330. That is, the time domain distance betweenthe m-th discovery signal block and the (m+1)-th discovery signal blockis 0, and the time domain distance between the m-th PRACH block and the(m+1)-th PRACH block is 0.

Also, FIG. 17 as the exemplary embodiment of the method M320 illustratesa case in which the time offsets {T_(G,m)} between the discovery signalblock and the PRACH block are all the same. That is, the time domaindistance between the m-th discovery signal block and the m-th PRACHblock is T_(G).

For this, the time duration of each discovery signal block and the timeduration of each PRACH block may be designed to be the same as T_(B).

In contrast, {T_(S,m)} and {T_(R,m)} may not be defined in the technicalspecification, but the base station may arbitrarily determine the{T_(S,m)} and {T_(R,m)} values. This is referred to as a method M331.For example, the base station may determine the time distance betweenthe m-th discovery signal block and the (m+1)-th discovery signal blockbased on traffic conditions. Accordingly, the base station maydynamically adjust a DL part and a UL part. Also, the base station mayarbitrarily determine the time distance between the m-th PRACH block andthe (m+1)-th PRACH block. In the method M331, the time distance betweenthe m-th discovery signal block and the (m+1)-th discovery signal blockmay be generally expressed as an integer number of OFDM symbols. If itis assumed that the number of OFDM symbols constituting a discoverysignal block is N_(DS), the time distance between the m-th discoverysignal block and the (m+1)-th discovery signal block may be an integermultiple of N_(DS).

FIG. 18 is a view showing a discovery signal and a PRACH resourcecomposition based on a method M321 and a method M331 according to anexemplary embodiment of the present invention.

In detail, FIG. 18 illustrates of a case of M=4. That is, four discoverysignal blocks and four PRACH blocks exist within one cell searchbandwidth.

FIG. 18 as the exemplary embodiment of the method M331 illustrates acase in which {T_(S,m)} has different values according to m and{T_(R,m)} is 0 for all m. That is, the time domain distance between them-th discovery signal block and the (m+1)-th discovery signal block hasdifferent values according to m. The time domain distance between them-th PRACH block and the (m+1)-th PRACH block is 0 regardless of m.

Also, FIG. 18 as an exemplary embodiment of the method M321 illustratesa case in which {T_(G,m)} may have the different values according to m.That is, the time domain distance between the m-th discovery signalblock and the m-th PRACH block has the different values according to m.

According to the method M331, as the base station has some degree offreedom in the resource configuration of the discovery signal block andthe resource configuration of the PRACH block, the base station mayflexibly operate the entire resource. For example, as illustrated inFIG. 18, in a case of the traffic condition in which the downlinktransmission and the uplink transmission must be quickly crossed intothe subframe unit (for example, the DL subframe->the UL subframe->thespecial subframe->the special subframe->the UL subframe), as the basestation disperses and allocates the discovery signal block and the PRACHblock at the appropriate positions within one periodicity, the resourcemay be efficiently managed.

Also, the method M331 is more advantageous than the method M330 in termsof forward compatibility. {T_(G,m)}, {T_(S,m)}, and/or {T_(R,m)} mayhave the fixed value for all periodicities of the discovery signaloccasion or may have different values for each periodicity. When theposition of the resource is changed over different periodicities of thediscovery signal occasion, RRM measurement accuracy of the terminal maydecrease. Accordingly, although the base station arbitrarily determinesthe parameters (for example, T_(G,m), T_(S,m), and T_(R,m)), changingthe resource position over different periodicities by the base stationmay be limited. For example, the parameter (for example, T_(G,m),T_(S,m), T_(R,m), etc.) may have the same value for every periodicity ofthe discovery signal occasion. That is, the parameter (for example,T_(G,m), T_(S,m), T_(R,m), etc.) may be applied as the same value forevery periodicity of the discovery signal occasion.

Meanwhile, when the terminal performs the random access, to satisfyvarious uplink coverage requirements, a plurality of PRACH formats maybe used.

In general, as a size of the time-frequency resource of the PRACHincreases, the random access coverage and the access collisionprobability between terminals are improved. The plurality of PRACHformats used in the LTE have the same bandwidth, however, the pluralityof PRACH formats have different time domain resource lengths from eachother according to the numerology or the repetition of the preamblesequence.

Similarly in the NR, because there are requirements for the variouscoverage and the access attempt probability, the plurality of PRACHformats are necessary.

For example, in the case of the small cell, because the coverage issmall and the number of terminals attempting access is small, the shortrandom access preamble may be required. Also, like the method M310, whenthe M PRACH resources exist and the terminal tries the access in onePRACH resource among the M PRACH resources, the probability of theaccess collision further decreases in each PRACH resource. In contrast,in the case of the micro cell or the small M value in the method M310,because the coverage is wide and the access collision probabilityincreases, a long random access preamble or repeated transmission may berequired.

When the plurality of PRACH formats exist, the base station may transmitthe PRACH format to the terminal through the discovery signal. This isreferred to as a method M340. The terminal may generate the randomaccess preamble according to the obtained PRACH format through thediscovery signal reception and may transmit the random access preambleon the PRACH resource. The PRACH format or the PRACH resourceconfiguration information may be transmitted through the PBCH as asystem information rather than through the synchronization signal or theBRS. For example, the base station may transmit at least one among aplurality of PRACH formats to the terminal through the PBCH included inthe discovery signal block.

The above-described discovery signal, the PRACH resource configurationmethod, and the initial access procedures may be applied for anynumerology. In the case that the carrier consists of a plurality ofnumerologies, like the case of the above-described synchronizationsignal, the plurality of numerologies may share the common discoverysignal and PRACH. In this case, for the numerology of the discoverysignal, the method M221 or the method M222 may be applied.

Also, the discovery signal and the PRACH may be defined for eachnumerology within one carrier. In this case, for the numerology of thediscovery signal, the method M231, the method M232, or the method M233may be applied. The numerology of the PRACH may be the same as thenumerology of the discovery signal, or a separate numerology for thePRACH may be used.

FIG. 19 is a view showing a computing apparatus according to anexemplary embodiment of the present invention. A computing apparatusTN100 of FIG. 19 may be the base station or the terminal described inthe present specification. Also, the computing apparatus TN100 of FIG.19 may be a wireless apparatus, a communication node, a transmitter, ora receiver.

In the exemplary embodiment of FIG. 19, the computing apparatus TN100includes at least one processor TN110, a transceiver TN120 connected toa network and performing the communication, and a memory TN130. Also,the computing apparatus TN100 may further include a storage apparatusTN140, an input interface apparatus TN150, an output interface apparatusTN160, etc. The constituent elements included in the computing apparatusTN100 are connected to each other by a bus TN170 to perform thecommunication with each other.

The processor TN110 may execute a program command stored in at least oneof the memory TN130 and the storage apparatus TN140. The processor TN110may mean a central processing unit (CPU), a graphics processing unit(GPU), or a dedicated processor performing the methods according to anexemplary embodiment of the present invention. The processor TN110 maybe configured to realize the procedure, the function, and the methodsthat are described in relation to an exemplary embodiment of the presentinvention. The processor TN110 may control each constituent element ofthe computing apparatus TN100.

Each of the memory TN130 and the storage apparatus TN140 may storevarious information related to the operation of the processor TN110.Each of the memory TN130 and the storage apparatus TN140 may be composedof at least one of a volatile storage medium and a non-volatile storagemedium. For example, the memory TN130 may be composed of at least one ofa read-only memory (ROM) and a random access memory (RAM).

The transceiver TN120 may transmit and receive a wire signal or awireless signal. Also, the computing apparatus TN100 may have a singleantenna or a multi-antenna.

The exemplary embodiments of the present invention are not only embodiedby the above-mentioned method and apparatus. Alternatively, theabove-mentioned exemplary embodiments may be embodied by a programperforming functions that correspond to the configuration of theexemplary embodiments of the present invention, or a recording medium onwhich the program is recorded. These embodiments can be easily devisedfrom the description of the above-mentioned exemplary embodiments bythose skilled in the art to which the present invention pertains.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

The invention claimed is:
 1. A method for transmitting discoverysignals, performed by a base station operating a cell, the methodcomprising: generating M discovery signal blocks, each of the Mdiscovery signal blocks including a primary synchronization signal(PSS), a secondary synchronization signal (SSS) and a physical broadcastchannel (PBCH), and a reference signal for demodulation of the PBCH,wherein M is a natural number equal to or greater than 1; determining afrequency resource for transmitting the M discovery signal blocks as oneof candidate frequency resources in a frequency band to which the cellbelongs; and transmitting the M discovery signal blocks through thedetermined frequency resource, wherein a frequency location of each ofthe candidate frequency resources is derived by each of frequencyreference points, and a spacing of frequency reference points is definedas an integer multiple of a subcarrier spacing.
 2. The method accordingto claim 1, wherein the each of the frequency reference points indicatesa center frequency location of the each of the candidate frequencyresources.
 3. The method according to claim 1, wherein the subcarrierspacing is one of subcarrier spacing(s) used for transmitting thediscovery signals in the frequency band.
 4. The method according toclaim 1, wherein the spacing of the frequency reference points isfurther defined as an integer multiple of a bandwidth of a resourceblock (RB) consisting of subcarriers based on the subcarrier spacing. 5.The method according to claim 4, wherein the RB consists of 12subcarriers.
 6. The method according to claim 1, wherein the spacing ofthe frequency reference points for a higher frequency band is wider thanthe spacing of the frequency reference points for a lower frequencyband.
 7. A method for receiving discovery signals, performed by aterminal, the method comprising: receiving a primary synchronizationsignal (PSS) among M PSSs constituting M discovery signal blocks throughone of candidate frequency resources in a frequency band to which a cellbelongs, each of the M discovery signal blocks including a PSS, asecondary synchronization signal (SSS) and a physical broadcast channel(PBCH), and a reference signal for demodulation of the PBCH, wherein Mis a natural number equal to or greater than 1; receiving a SSS, a PBCH,and a reference signal for demodulation of the PBCH through the one ofthe candidate frequency resources where the terminal received the PSS,wherein a frequency location of each of the candidate frequencyresources is derived by each of frequency reference points, and aspacing of frequency reference points is defined as an integer multipleof a subcarrier spacing.
 8. The method according to claim 7, wherein theeach of the frequency reference points indicates a center frequencylocation of the each of the candidate frequency resources.
 9. The methodaccording to claim 7, wherein the subcarrier spacing is one ofsubcarrier spacing(s) used for transmitting the discovery signals in thefrequency band.
 10. The method according to claim 7, wherein the spacingof the frequency reference points is further defined as an integermultiple of a bandwidth of a resource block (RB) consisting ofsubcarriers based on the subcarrier spacing.
 11. The method according toclaim 10, wherein the RB consists of 12 subcarriers.
 12. The methodaccording to claim 7, wherein the spacing of the frequency referencepoints for a higher frequency band is wider than the spacing of thefrequency reference points for a lower frequency band.